Should I buy a new mac or upgrade my current one?

I have a mid 2010 baseline macbook pro. My battery is beginning to die on me as I have used 600 cycles, my hdd is slow and i think i need more ram.

I don't know whether to upgrade my hd to an ssd, upgrade my battery and ram or to just buy a new mac. If I don't upgrade my mac now, I will buy a new one with in the next 2 years as I love the retina display of the new macs and my mac will be about 4.5 - 5 years old. I also need an HDMI port and don't want to buy an adaptor for my Mini display port.

So should I just buy a new one or upgrade the internals or wait a few years???